Dental amalgam :
The dental filling material whose use hase spread after a 1850 discovery in China was dated 4 th century B.C.
This material involves the mixture of several metals including silver copper, tin and sometines zinc and beryllium associated with about 1 gram of Mercury.
This plastic material is then inserted into the carious cavity after removal of any infected dentine. Metal hardening and crystallization are almost immediate.
The mercury release into the oral cavity after brushing and chewing was analyzedand measured and attained significant rate.
The controversy regarding the harmfulness of this material is still relevant.
Today OMS dictate a number of recommendations and precautions in the use of this specific material in pregnant women and in infants.
Some countries have banne dits use (Sweden, Japan)
The evolution of this material mouth is related to salivary context and changes in pH (acidity) of the mouth.
Nevertheless, within 10 years after installation, sometimes earlier, we routinely note of visible corrosion points and / or chipping of the sealing edges more or less important depending on the presence or not of other metals in the mouth (bimetallism)
The consequence of this aging induced percolation of shutter and recurrence of disease caries (decay of recovery)
We can notice then, there is a gray and / or blue of the tooth due to oxidation of the silver present in the amalgam (silver oxide is black). Indeed, the internal surfaces of the amalgam oxidized (so black) in direct contact with dentin and translucent enamel give the impression that the tooth is darker.
The treatment of this recovery carious disease involves a new curettage of infected dentine and puts increasingly threaten the conversation of pulp vitality because curettage dentin reinfected leaves fewer nerve protection in dentin the tooth.
Often after the 2nd or 3 rd reprocessing the tooth should be pulped (devitalized)
Moreover, despite all the virtuosity of the operator, the proximal surfaces of the tooth restored with this material are rarely optimal :
– Point of contact interdental difficult to reproduce (bio-tooth shape) which commonly leads interdental food settlements.
– Surface state (polishing) of this point of often very rough contact there by retaining the cariogenic bacteria and prohibiting prophylactic flossing.
The consequance is that it is very common for removal of amalgam to discover caries on the contact surfaces of adjacent teeth

The composite :
Alternative to amalgam
Consists of a plastic resin, mercury free, inserted within the carious cavity, curing by a polymerization reaction initiated by a specific wavelenght of light (lamp light cure of blue color)
This polymerization reaction is effected by the chemical interaction between the monomer and the polymer contained in this material.
To improve strength characteristics, abrasion of the ceramic powder charges were added in the composition of these products in recent years.
The difficulty of the implemantation of this material is to accomplich complete polymerization of all the inserted material, which must be performed in optimal conditions, protected from moisture in detal and surgical fields with the help of a formwork matrix.
More carious cavity is large, more the deep part of the mass of material to polymerize becomes uncertain.
When polymerization is complete, the composite is the seat of a release of monomer molecules composed allergenic. The shutter is not completely waterproof and decay times follow.
More decay is large, that is to say, the more tooth surfaces is important to restore knowing that healthy tooth has five surfaces, it will be more difficult to accomplish optimal polymerization on all restoration surfaces the composite.
Restorations with composite resin carious lesions of 2 sides and have low durability of poor prognosis in 5 to 10 years.
The chemical strucutre of these resinous materials induces a microscopically porous outer surface. These micropores are quickly contaminated by the bacteria of the oral flora.
Therefore the composite and tarnishes the initial color darkens.

The seals will be colored and reveal signs of seepage. Upon removal by milling of these composite materials, there is frequently a characteristic odor of the presence bacteria.
By their constitution, these materials are avoided in restoration of lesions in or juxta-gingival.
Indeed, when the composite is in direct contact with the gums, it regularly finds chronic periodontal inflammation. This irritation is related to the microscopic surface porosity which retains much bacterial plaque that tooth enamel.